Control element for injectors with switchable nozzle needle

ABSTRACT

The invention relates to a device for actuating a control piston or nozzle needle ( 27 ) via a control chamber ( 26 ). The control chamber communicates via a control chamber line ( 25 ) with valve chambers ( 3, 22 ) of a 3/2-way valve ( 5 ). The valve body ( 6, 40, 51 ) of this valve is switchable by means of an actuator ( 11 ). By means of a restoring spring ( 14 ), the valve body ( 6, 40, 51 ) is acted upon such that a seat portion ( 7 ), embodied in the housing ( 4 ) on the valve body ( 6, 40, 51 ), is put into its valve seat ( 20 ). The valve body ( 6, 40, 51 ) of the 3/2-way valve ( 5 ) has a seat portion ( 7 ) and a longitudinal slide portion ( 8 ), as well as hydraulic faces ( 31,32 ), facing one another, that make the state of pressure equilibrium of the valve body ( 6, 40, 51 ) possible. The valve body ( 6, 40, 51 ) is moved to different stroke lengths ( 10; 23, 24 ) by means of an actuator ( 11 ).

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a 35 USC 371 application of PCT/DE 02/04387 filed onNov. 29, 2002.

BACKGROUND OF THE INVENTION

1. Field of the Invention

In air-compressing internal combustion engines, fuel injection systemsare increasingly being used that for instance include injectors that aresupplied with fuel via a high-pressure collection chamber (common rail),or injectors with pressure boosters or unit fuel injector systems. Thefuel injection systems listed predominantly include 2/2-way valves,which as a rule are not in a state of pressure equilibrium.

2. Prior Art

European Patent Disclosure EP 0 987 431 A2 has a fuel injector forinternal combustion engines as its subject. The fuel injector includes anozzle needle, which is vertically movably received inside a bore in theinjector housing. One face of the nozzle needle partly defines a controlchamber, which communicates with a supply line via a restriction. Bymeans of a control valve, the communication between the control chamberand a low-pressure region is controlled. There is also a valve forcommunication between the supply line and the low-pressure region. Thisvalve and the control valve each include armature elements, which areactuatable by means of an electromagnetic actuator that is common toboth valves.

European Patent Disclosure EP 1 081 373 A2 likewise has a fuel injectoras its subject. It is used in an arrangement that includes a fuel pump,a pump chamber, and a first valve; this first valve controls thecommunication between the pump chamber and a low-pressure region. Theinjector includes a nozzle needle, which can be brought into interactionwith a needle seat. A control chamber is disposed such that the fluidpressure prevailing in it presses the nozzle needle into its needleseat. The fluid pressure inside the control chamber is controlled bymeans of a control valve. The control valve in turn is controlled via anactuating assembly in such a way that when the actuating assembly is notactivated, the control valve opens a fluid communication between thecontrol chamber and the low-pressure region.

In the version of EP 1 081 373 A2, 2/2-way valves are used on the outletside relative to a control chamber. The use of such 2/2-way valves onthe inlet side of a control chamber, which acts upon a control pistonthat indirectly actuates the nozzle needle, is unfavorable because ofthe high actuation forces required.

SUMMARY OF THE INVENTION

The valve proposed according to the invention furnishes apressure-balanced 3/2-way valve, which requires only slight actuatingforces compared to the versions known from the prior art. The versionproposed according to the invention can therefore be disposed especiallyadvantageously on the high-pressure side upstream of the control chamberof a control piston that indirectly actuates the nozzle needle, ordirectly upstream of the control chamber. In an advantageous feature ofthe valve body of the 3/2-way valve, this valve body includes a slideportion and a seat portion, whether the valve body of the 3/2-way valveis used in an arrangement as an inward-opening valve or in anarrangement as an outward-opening valve.

If the 3/2-way valve is used on a control piston by way of which thenozzle needle is controlled, and if this control piston is subjected topressure, then the injection nozzle can also be put under pressure. Bymeans of the 3/2-way valve, the control of the pressure can be done viathe control piston. Both the valve body of the 3/2-way valve in theinward-opening valve version and the valve body of 3/2-way valves in theoutward-opening valve version are provided with hydraulic facesconfigured such that a state of pressure equilibrium of the valve bodyis made possible. The state of pressure equilibrium of the valve bodymakes it possible to use only slight actuating forces; that is, thevalve bodies configured according to the invention can be moved by meansof a magnet valve, without the interposition of a pressure booster forincreasing the stroke lengths. The valve bodies furthermore each includeone seat portion and one longitudinal slide portion. By means of theseat portion of the valve bodies, the high-pressure side of the 3/2-wayvalve can be closed, so that no pressure losses occur.

The valve bodies have a low mass and therefore make the shortestpossible switching times possible; the achievement of short switchingtimes is further reinforced by the state of pressure equilibrium of thevalve bodies. Particularly when the 3/2-way valve is used in theinward-opening valve arrangement, the opening motion of the valve needleis reinforced, since in this arrangement the valve body opens into thepressure chamber.

The structural form of the valve body, with a seat portion and alongitudinal slide portion, makes simple large-scale mass production ofthe valve body possible.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described in further detail below in conjunction withthe drawings, in which:

FIG. 1, shows a variant embodiment of a 3/2-way valve in anoutward-opening valve arrangement, that is, moving out of a pressurechamber;

FIG. 2, a further variant embodiment of a 3/2-way valve in anoutward-opening valve arrangement;

FIG. 3, the schematic hydraulic circuit diagram of the further variantembodiment of FIG. 2; and

FIG. 4, the variant embodiment of a 3/2-way valve in an inward-openingvalve arrangement, that is, moving into a pressure chamber.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a variant embodiment of a 3/2-way valve, which is embodiedin an outward-opening valve arrangement and which actuates a controlpiston that acts upon the nozzle needle.

In the arrangement shown in FIG. 1, a control chamber 26, which actswith pressure upon a control piston 27, is pressure-relieved or actedupon by pressure by means of a 3/2-way valve 5. Via the indirectactuation of a nozzle needle via the control piston 27, a closure of thenozzle needle can also be accomplished under pressure, which can bedesirable in injection events.

Via a high-pressure inlet 1, which discharges at a discharge point 34into an annular chamber 3, the annular chamber is acted upon withpressure by fuel that is at high pressure from the high-pressurecollection chamber (common rail), not shown, of an injection system.Instead of the common rail, the high-pressure inlet 1 can also be actedupon directly via a high-pressure pump. The high-pressure inlet 1 can beprovided with an inlet throttle 2—as schematically indicated in FIG. 1.The annular chamber 3 is embodied inside the housing 4 of an injectorbody.

The variant embodiment shown in FIG. 1 of a 3/2-way valve 5 includes avalve body 6, which has both a seat portion 7 and a longitudinal slideportion 8. The seat portion 7 is located above the longitudinal slideportion 8. Above the seat portion 7 in the valve body 6 an armatureplate 9 is embodied on the valve body 6, forming the end face of thevalve body 6. Above the armature plate 9 and spaced apart from it by agap size 10 (h) is a coil housing 12, which receives an annularlyconfigured magnet coil 11. The coil housing 12 further includes asleevelike insert 13, which surrounds a compression spring 14. Thecompression spring is braced on the upper end of the coil housing 12 byan adjustment disk 15, which is let into the interior of the sleevelikebody 13. The other end of the compression spring 14, preferably embodiedas a spiral spring, is braced on a contact face 16 of the armature plate9, which is spaced apart by the gap size 10 (h) from the face end of themagnet coil 11 in the coil housing 12. The gap size 10 is composed ofone component 10.1 (h₁) and a second component (h₀), identified byreference numeral 10.2; h_(RL) designates that component of the gap size10 that results from the requisite remanent air gap. While h₁ designatesthe prestroke until the control edges are at the same level and asealing action results, the second component h₀ represents the amount ofoverlap. The total stroke is composed of both components h₁ and h₀.

The seat portion 7 of the valve body 6 in the variant embodiment of the3/2-way valve 5 is surrounded inside the housing 4 by a recess 21 ofcuplike configuration. Above the cuplike recess 21, a low-pressureoutlet 17, oriented laterally from the armature plate 9, branches off,and through it, a diverted fuel volume flows out into the low-pressureregion of the fuel injection system, such as the vehicle tank. The seatportion 7 of the valve body 6, has a seat diameter 18 which cooperateswith a seat face 19, embodied in the housing 4, of a valve seat 20. Bymeans of the seat portion 7, an annular chamber 22 can be sealed offbelow the seat portion 7, so that no pressure losses on thehigh-pressure side can occur in the low-pressure region 17 of the3/2-way valve 5. The annular chamber 22 extends inside the housing 4 ofthe 3/2-way valve 5 from the seat portion 7 as far as a control edge forthe longitudinal slide portion 8. The longitudinal slide portion 8 inincludes a slide portion length 30, having diameter equivalent to theseat diameter 18 in the lower region of the seat portion 7 of the valvebody 6. The hydraulic faces 31 and 32 that define the annular chamber 22inside the housing 4 of the 3/2-way valve 5 are identical in terms oftheir hydraulic areas, so that the valve body 6 of the 3/2-way valve ispressure-balanced. A control chamber line 25 also branches off from theannular chamber 22 inside the housing 4; in the view of the variantembodiment shown in FIG. 1, it is embodied without a throttlerestriction. The control chamber line 25 discharges into the controlchamber 26 at a control chamber wall 29. The control chamber 26, whichis likewise embodied in the housing 4, encloses an upper face end 28 ofa control piston 27, with which a nozzle needle, not shown here, isindirectly actuatable.

The annular chamber 3 embodied in the housing 4 encloses thelongitudinal slide portion 8 of the valve body 6, and a recess is letinto the upper region of the annular chamber 3. The hydraulic face 32that forms the slidelike control edge plunges into this recess when themagnet coil 11 is triggered. The total stroke of the valve body 6,composed of the portions h₁ and h₀, is traversed as fast as possible.Supplying electric current to the magnet coil 11 attracts the armatureplate 9, and the valve body 6 is moved upward. The first gap size 10.1,corresponding to an opening stroke length h₁ (reference numeral 24) isspanned upon excitation of the magnet coil 11, so that the seat portion7 moves out of its valve seat 20, and pressure from the control chamber26 escapes into the low-pressure line 17. The outflow quantity canoptionally be limited by a throttle, not shown here. In the furtherstroke of the armature plate 9 of the valve body 6 corresponding to asecond portion of the gap size 10.2, that is, corresponding to thestroke length h₀ (see reference number 23, overlapping stroke h₀), thecontrol chamber, embodied in the housing 4, overlaps with the controlchamber of the hydraulic face 32 embodied in the upper portion of thelongitudinal slide portion 8. Depending on the overlap 23 h₀ set, thehigh pressure, which prevails in the annular chamber 3 from thehigh-pressure source via the high-pressure inlet 1, is completely closedoff. Any leak from the high-pressure inlet that occurs has no influenceon the behavior of the control chamber, since the opened cross sectionof the seat portion 7 in the upper region of the valve body 6 of the3/2-way valve 5 is very large by comparison.

When the magnet coil 11 is switched off by a control unit, not shown inFIG. 1, the restoration of the valve body 6 into the zero positionoccurs. This is attained by means of the restoring spring 14, which actsupon the stop face 16 embodied on the armature plate 9 and restores thevalve body 6 again in the variant embodiment of the 3/2-way valve 5 ofFIG. 1.

The variant embodiment shown in FIG. 1 of the 3/2-way valve 5 isselected in an outward-opening valve arrangement 43, in which the valvebody 6 opens, moving outward from the pressure chamber, in this case theannular chamber 3. The variant embodiment shown in FIG. 1 of the 3/2-wayvalve 5 is pressure-balanced in the switching positions; that is, thehydraulic faces 31 and 32 on the valve body 6 that are operative and areexposed to the pressure, and the resultant forces, cancel one anotherout in their action, so that by the use of electromagnets containingmagnet coils 11, fast, short switching times are attainable, givenadequate strokes.

FIG. 2 shows a further variant embodiment of a 3/2-way valve, again inan outward-opening valve arrangement.

In the variant embodiment shown in FIG. 2 of a 3/2-way valve 5, the seatportion 7 and the longitudinal slide portion 8 on the valve body 40 aretransposed—compared to the illustration in FIG. 1.

In the further variant embodiment in FIG. 2. the high-pressure inlet 1discharges in the annular chamber 3 of the housing 4. The annularchamber 3 is adjoined inside the housing 4 by the annular chamber 22.From the annular chamber 22, a control chamber line 25 branches off at adischarge point 35; this line can optionally include a throttlerestriction 48. The control chamber line 25 discharges within thecontrol chamber wall 29 into the control chamber 26, which is partlybounded by the end face 28 of the control piston 27.

In the further variant embodiment of FIG. 2, the coil housing 12 withthe magnet coil 11 let into it is located in operation above the annularchamber 3. Analogously to the variant embodiment of FIG. 1, a gap size10, which includes a first gap size portion 10.1 and a second gap sizeportion 10.2 (analogously to the variant embodiment of FIG. 1), isestablished between an armature plate 9, communicating with the valvebody 40, and the face end toward the armature plate of the magnet coil11; h_(RL) designates the remanent air gap. A tapered region of thevalve body 40 is surrounded by a compression spring 14, which is bracedby one end on a part of the valve body 40 that receives the armatureplate 9, while the other end of the restoring spring 14 rests on aspring prestressing force adjusting disk 41 that is inserted into acentral bore of the magnet coil housing 12.

To stabilize the central position of the valve body 40, one or moregrooves are embodied between the spring prestressing force adjustingdisk 41 and the annular chamber 3, on the circumferential surface of thevalve body 40.

Analogously to the view of the variant embodiment of FIG. 1, in thevariant embodiment of the 3/2-way valve 5 in FIG. 2, the annular chamber3 in the housing 4 is essentially penetrated by the longitudinal slideportion 8, on which a conically configured hydraulic face 32 is embodiedthat moves into a bore inside the housing. This hydraulic face 32 of thelongitudinal slide portion 8 is located opposite a seat portion 7 on thelower end of the valve body 40, and this seat portion in turn includes ahydraulic face 31. By means of the seat portion 7, the valve seat 20 isclosed in accordance with the stroke of the valve body 40 inside thehousing 4 that is adjusted by the magnet coil 11, so that an outflow ofhigh pressure via the annular chamber 22 into a leak fuel outlet 44 isprecluded. A platelike insert 47 is shown below the face end of the seatportion 7; it prevents the maximum stroke, that is, a vertical strokemotion of the valve body 40 inside the housing 4 that exceeds the gapsize 10.

Depending on the excitation of the magnet coil 11, that is, on theintensity of the magnetic force, the valve body 40 moves into the boreinside the housing 4. In an inward motion corresponding to the first gapsize portion 10.1, opening of the valve seat 20 in the seat portion 7 ofthe valve body 40 takes place, so that the control chamber 26 isrelieved toward the leak fuel side. A downward motion of the valve body40 of the 3/2-way valve 5 follows, in the further variant embodiment inFIG. 2, in the direction of the insert 47 that defines the maximumstroke. In a vertical downward motion corresponding to the second gapsize portion 10.2, an overlap at an overlap stroke length 23 (h₀) occursbetween the seat slide portion 8, or the hydraulic face 32 embodied onit, and a control edge 46 of the housing. The edge 45 of the hydraulicface 32 in the lower region of the seat slide portion 8 of the valvebody 40 seals off the high-pressure inlet 1 and the annular chamber 3,from the annular chamber 22 inside the housing 4 upon an overlap of thecontrol edge 46 of the housing corresponding to the overlapping stroke23. If the magnet coil 11 in the coil housing 12 is switched off, therestoration of the valve body 40 follows because of the action of therestoring spring 14, which is let in between the armature plate 9 andthe support disk 41 on the housing 4 and moves the seat portion 7,embodied in the lower region of the valve body 40, into its seat face 19toward the housing. In this zero position of the 3/2-way valve 5, in thevariant embodiment of FIG. 2, the leak fuel outlet 44 is closed.

The further embodiment, shown in FIG. 2, of a 3/2-way valve is alsoembodied as an outward-opening valve arrangement; that is, the valvebody 40 opens from a pressure chamber, in the present case the annularchamber 3, inside the housing 4. To bring about a pressure equilibrium,the seat diameter 18 of the seat portion 7 of the valve body 40 and thediameter of the longitudinal slide portion 8 of the valve body 40 matchone another.

FIG. 3 shows the schematically simplified hydraulic circuit diagram ofthe further variant embodiment of FIG. 2 as well as throttlerestrictions that can optionally be provided.

In FIG. 3, the 3/2-way valve is shown as a schematic block circuitdiagram. A throttle restriction 2 is optionally associated with thehigh-pressure inlet 1, and like the control chamber lead line 25opposite it, a throttle restriction 48 that can optionally be providedcan be integrated, with which during the pressure relief of the controlchamber 26 into the low-pressure region 17, the outflowing fuel quantitycan be limited. The control chamber line 25 discharges into the controlchamber 26 at an upper boundary wall 29. The control chamber 26 ispartly defined by the end face 28 of the control piston 27, or of anozzle needle. In the embodiment of the control piston 27 as a pistonpreceding the nozzle needle, the nozzle can remain closed, or can beclosed under pressure. The control of the pressure via the piston 27 isthe task of the 3/2-way valve 5. In the view in FIG. 3, the low-pressureoutlet 17 is also shown, by way of which a diversion quantity flowingout from the control chamber 26 flows back into a low-pressure region,shown here only schematically, of a motor vehicle, such as a fuel tank.

FIG. 4 shows the variant embodiment of a 3/2-way valve in aninward-opening valve arrangement, that is, a valve that moves into thepressure chamber.

In this variant embodiment of an inward-opening valve arrangement 50 ofa 3/2-way valve 5, its seat portion 7 and its longitudinal slide portion8 are located jointly in the lower end region of a valve body 51 of the3/2-way valve 5. A magnet coil 11 that is surrounded by a coil housing12 is received in the upper region of the valve body 51. An armatureplate 9 of the valve body 51 is spaced apart from the lower face end ofthe magnet coil 11 by a gap size 10(h). The total stroke between theface end of the magnet coil 11 pointing toward the armature plate andthe armature plate 9 itself is represented by the double arrow 10 and iscomposed of a first gap size 10.1 and a second gap size 10.2. The firstgap size 10.1 corresponds to the opening stroke h₁, or be overlap 23,while the second gap size 10.2, also shown, corresponds to the strokeh₀.

In the middle region of the valve body 51 of the 3/2-way valve 5 in theinward-opening valve arrangement 50, hydraulic faces 31 and 32 face oneanother on either side of an annular chamber 22 inside the housing 4.Because the hydraulic faces 31 and 32 are embodied with an identicalarea, a state of pressure equilibrium of the valve body 51 of the3/2-way valve 5 is attainable, making the tiniest adjusting forces andthe shortest switching times possible.

In this variant embodiment, the relief of the control chamber 26 to thelow pressure 17 via the control lead line 25 is initiated upontriggering of the electromagnet 11, acting as an actuator, by an openingstroke h₁ (reference numeral 24). In this state, the conical seat 52 inthe lower region of the valve body 51 opens, while the high-pressureinlet is closed by upward motion of the hydraulic face 32 in the upperregion of the longitudinal slide portion 8 of the valve body 51 into theannular chamber 22 the high-pressure inlet 1. The greater the amount ofthe overlap 24 h₀, the tighter is the closure of the valve chambers 3against the prevailing high pressure. If upon excitation of the magnetcoil lithe valve body 51 is opened in accordance with the opening strokeh₁ (reference numeral 24), then the seat diameter 18 of the conical seat52 moves upward in the annular chamber 3, so that fuel is capable offlowing out from the control chamber 26 into the low-pressure region 17,via the control chamber line 25 and the annular chamber 3.

The inward-opening valve arrangement 50, shown in FIG. 4, of the 3/2-wayvalve 5 configured according to the invention moreover enables anopening into the pressure chamber, thus reinforcing the opening motionsof valve needles or the control piston 27, which additionally shortensthe switching times.

In both variants, that is, the outward-opening valve arrangement 43 andinward-opening valve arrangement 50 ,the valve bodies 6, 40, 51 in thevarious switching positions of the 3/2-way valve 5 arepressure-balanced. The respective faces 31, 32 exposed to the pressureand the resultant adjusting forces cancel one another out in theireffect. The actuation of the proposed 3/2-way valve 5 can be effected onthe one hand by an actuator, which is embodied as a magnet coil 11, oron the other, it is quite possible to use further fast-switchingactuators, such as piezoelectric actuators. In piezoelectric actuators,to assure an adequate stroke 10 to cover the opening stroke h₁ (24) andthe overlapping stroke h₀ (reference numeral 23), a boost in terms ofattaining the requisite stroke length must be assured, for instance inthe form of a pressure booster or the like.

The 3/2-way valves 5 of the kind according to the invention can be usedin injectors of the kind where the nozzle needle stroke is controlled,such as common rail injectors or unit fuel injectors.

The foregoing relates to preferred exemplary embodiments of theinvention, it being understood that other variants and embodimentsthereof are possible within the spirit and scope of the invention, thelatter being defined by the appended claims.

1. In a device for actuating a control piston or nozzle needle (27), viaa control chamber (26), which communicates via a control chamber line(25) with valve chambers (3,22) of a 3/2-way valve (5), whose valve body(6, 40, 51) is switchable by means of an actuator (11) and is moreoveracted upon by pressure by means of a restoring spring (14), and a seatportion (7) in the housing (4) embodied on the valve body (6, 40, 51) isput into its valve seat (20), the improvement wherein the valve body (6,40, 51) of the 3/2-way valve (5) comprises a seat portion (7), alongitudinal slide portion (8), and opposing faces (31, 32) on the valvebody which make the state of pressure equilibrium of the valve body (6,40, 51) possible, the actuator (11) being operable to move the valvebody (6, 40, 51), different stroke lengths (10.1, 10.2; 23, 24).
 2. Thedevice of claim 1, wherein the 3/2-way valve (5) is disposed upstream ofthe control chamber (26) relative to the high-pressure inlet (1).
 3. Thedevice of claim 1, wherein the 3/2-way valve (5) is built in in anoutward-opening valve arrangement (43) in the housing (4).
 4. The deviceof claim 3, wherein the seat portion (7) and the longitudinal slideportion (8) are opposite one another on the valve body (6).
 5. Thedevice of claim 1, wherein the 3/2-way valve (5) is received in thehousing (4) in an inward-opening valve arrangement (50).
 6. The deviceof claim 5, wherein the seat portion (7) and the longitudinal slideportion (8) are embodied jointly in the lower region of the valve body(51).
 7. The device of claim 6, further comprising a seat face (19),which cooperates with a conical seat (52) inside the housing (4),embodied on the seat portion (7) of the valve body (51).
 8. The deviceof claim 5, wherein within a first stroke length h₁ (24) of the valvebody (6, 40, 51), the control chamber (26) is relieved on thelow-pressure side.
 9. The device of claim 8, wherein within a secondstroke length h₀ (23), the high-pressure line (1) is disconnected fromthe valve chambers (3,22) of the 3/2-way valve (5).
 10. The device ofclaim 8, further comprising a throttle element (48) received in thecontrol chamber line (25) whereby during the pressure relief of thecontrol chamber (26), the outflowing quantity is limitable within thestroke length h₁ (24).
 11. The device of claim 1, wherein thelongitudinal slide portion (8) hydraulically disconnects an annularchamber (3) from an annular chamber (22).